1. Field of the Invention
The present invention relates to disk drives for information storage in computer systems, and more particularly to a suspension load beam for an actuator assembly.
2. Description of the Prior Art
Most disk drive storage systems include a plurality of disks stacked onto a rotatable spindle and a corresponding number of magnetic heads that read binary digital information from the disks and write such information on them. The magnetic heads are typically mounted on sliders that are positioned over the surfaces of the disks by rotary movement of the actuator.
A voice coil motor drives the actuator; and this motor typically includes permanent magnets mounted to the base member and a wire and bobbin coil assembly mounted on the actuator. The forces generated by the interaction between the input current of the coil assembly and the magnetic field of the permanent magnets drive the actuator to various positions over the disks.
The actuator assembly normally includes an actuator arm pivotally mounted to the base member with a pivot bearing cartridge, or other type of pivoting mechanism known in the art, a suspension load beam secured to an end portion of the arm, and a flexure secured to an end portion of the suspension load beam. The flexure supports the magnetic heads at a distal end, including read and write elements and a slider.
As performance and resonant frequency requirements have become more and more stringent, suspension load beam designs have become more and more complex, as have the methods of forming the suspension load beams. One design option used in making suspension load beams is the use of partial etching in certain areas of the suspension load beam. The process of partial etching, however, does not allow the requisite control to achieve close tolerances in the suspension load beam thickness. Variations as small as xc2x10.15 mil to xc2x10.25 mil in the thickness of the bend radius portion of a suspension load beam cause substantial variations in the spring rate, resonant frequencies, as well as other physical parameters of the beam. Substantial variation from the desired design parameters becomes a significant drawback in fabrication and results in low production yields.
The suspension load beam of the present invention and the method of producing it meets the most stringent performance and resonant frequency requirements. The method provides a solution to compensate the partial etched suspension load beams with loose tolerances in thickness, and it does so efficiently and inexpensively, maximizing the yield in production.
In accordance with one embodiment of the present invention, a suspension load beam for an actuator includes a bend radius portion with a spring rate that is less than 18 Newtons per meter, a first bending mode that is greater than 3,500 Hertz, and a first torsion mode that is greater than 5,300 Hertz. The method of making this suspension load beam includes etching a sheet of material to form the full suspension load beam profile including a partially etched bend radius portion, inspecting the bend radius portion to determine its thickness, and removing more material from the bend radius portion, and/or from the main body of the suspension load beam, to obtain close tolerances for the required performance.